Generally, the invention relates to contactless connectors for inductive power transmission. Contactless power connectors are widely utilized for their various advantages over conventional power connectors, namely for: high resistance to contact failures, an unlimited number of mating cycles, a low wear and tear, prevention from electric shocks, sparks and current leaks and their operability under dirty or harsh environments.
Specifically, known contactless connectors for power transmission may be used in a variety of industrial devices such as, for instance, robotics technology, rotary applications and molding equipment. Such known contactless connectors are required to be operable under hostile environ-mental influences, to resist a high amount of wear and tear during the mating cycles or may be used for power transmission in humid, explosive or combustible environments.
Known configurations of contactless power connector systems allow for transmission of electrical power between a contactless connector and a mating connector.
However, in case of inductively transmitting a higher power level, a considerable amount of heat has to be taken into account that is generated from eddy currents, for instance. Heat dissipation is thus an important aspect to resolve, which however results in a need for appropriate housing materials. Therefore, the outer housing may be of metal, which results in parts of the magnetic field lines tending to flow through the metal housing. Consequently, those field lines inside the housing lead to additional losses. Overall, due to the power losses at the inductive connector, the power transmission decreases.
But even if the housing is formed in a way that eddy currents caused by the actual inductive coupling element are reduced, the magnetic field caused by the leads that feed the inductive coupling element create a significant impact on the heat development due to power losses. In particular, the outer ferrite element will include some sort of base plate where through these contact leads are fed. Any current flowing through the contact leads causes magnetic field lines around the lead wire and consequently eddy currents in this base plate. These eddy currents in turn cause a heating of the connector which is not acceptable during operation.
From the standard specifications for ferrite pot style cores of the International Magnetics Association (IMA-STD-110 2011.03, found at http://www.adamsmagnetic.com/pdf/Standard-Spec-for-Ferrite-Pot-Style-Cores.pdf) there exist various forms of so-called pot cores which take into account the difficulties connected with the B-fields around the lead receiving passageway wires. These cores with their comparatively large openings in the cylindrical side wall, however, are not efficient enough for reducing power losses caused by the power transmitting inductive coupling element itself.
FIG. 1 shows the basic parts of a known contactless connector 100 that can be inductively connected to a corresponding mating connector. The known contactless connector 100 therefore has a mating end 101 for interacting with a belonging mating connector (which, however, is not depicted in the figures), so that a contactless power transfer and optionally also a signal transmission is possible. An inductive coupling element 110, in this example a coil having a plurality of windings 115, is provided for inductively transmitting energy to the corresponding mating connector. A first and a second contact lead 103, 104 feed the current to and from the windings 115.
An outer ferrite element 107 is provided and arranged so that it at least partially surrounds the inductive coupling element. This causes an improved guidance of the B-field towards the mating connector. For further guiding the B-field, a base plate 105 which also consists of a ferritic material is provided. For feeding the first and second contact leads 103, 104 through the ferritic parts, the base plate 105 includes two lead receiving passageways 108, 109.
Additional openings 106 for other components (such as an optical fiber or an antenna) may optionally be provided in the base plate 105. Furthermore, optionally also an inner ferrite element 102 that is inserted into the inductive coupling element 110 may be provided in the contactless connector 100 according to the invention. However, such an inner ferritic element 102 is not essential for the invention.
With respect to FIG. 2, the known contactless connector 100, as already mentioned above, show a disadvantage caused by the current flowing through the first and second contact leads 103, 104, as symbolized by the arrows 111, 112. In particular, a magnetic field is induced that is guided and short-circuited by the base plate 105. This B-field might saturate the ferrite of the base plate 105 and, in case that the current is alternating, additional excessive losses will occur.
Hence, there is a need for an improved contactless connector which remedies the aforementioned disadvantages.